Nichiro was converted by Nichiren in Kamakura (1254). When Nichiren was exiled to Sado Island, Nichiro was imprisoned. When Nichiren was pardoned, he took the letter of pardon to Sado and came back to Kamakura with his master. He became chief priest of the Myohonji Temple at Hikigayatsu, and the Hommon-ji Temple at Ikegami near Edo. Among his many disciples were Nichizo, Nichi- rin, Nichizen, Nichiden, Nichihan, Nichiin, Nitcho, Nikko and Rokei.
He was a nephew of Nissho.